Development of Constructive Taste Bud Expansion across Astyanax mexicanus Morphotypes

Abstract

By Halle Heerema, Biological Sciences

Advisor: Joshua Gross

Presentation ID: 214

Abstract: Constructive trait evolution, including numerical expansions of taste buds, has been minimally examined. We approach this problem in Astyanax mexicanus, a fish species with two distinct morphotypes - a cave-dwelling and a surface-dwelling morph. For my project, I analyzed key developmental stages of taste bud development, focusing on the expansion of taste buds across the head and chin of adult cave-dwelling individuals, not seen in surface fish. Our approach involves comparisons of both morphs at monthly intervals of development, from 6 months post-fertilization to 1 year. We labeled taste buds using fluorescent immunohistological staining for an antibody against calretinin, a calcium-binding protein enriched in mature taste buds. Following staining, a fluorescent stereomicroscope was used to image the stained taste buds, which will be processed to count and identify positioning of taste buds, using an automated program (NIH ImageJ). Our preliminary evidence suggests that by six months of age, taste buds of the cave morph have not yet expanded beyond the lingual region (still matching the surface morph). By 9 months however, the expansion has begun and appears to be at an intermediate stage beyond the area seen in surface fish taste buds but have not reached the adult cave fish pattern of distribution. Future directions for this work include analyses of quantitative genetic features of this trait, to identify QTL and candidate genes that may mediate taste system expansion. In sum, this work provides tissue-level insights to a remarkable constructive phenotype evolving under the intense environmental pressures of the cave.